1. Technical Field
The present disclosure relates to supplemental alert generation devices for supplementing the audible alert signals generated by smoke, fire, and/or carbon monoxide detectors.
2. Description of the Related Art
A variety of commercially available detector/alert devices exist for alerting individuals of the presence of smoke, heat, and/or carbon monoxide. These devices are typically designed to be mounted to the ceiling in various rooms of a house or other building, and are ordinarily powered by the building's AC power lines with battery backup. The audible alert signals generated by such devices are governed by various regulations such as Underwriters Laboratories (UL) 217 (“The Standard of Safety for Single and Multiple Station Smoke Alarms”), UL 464 (“The Standard of Safety for Audible Signal Appliances”), UL 1971 (“The Standard for Signaling Devices for the Hearing Impaired”), and UL 2034 (“The Standard of Safety for Single and Multiple Station Carbon Monoxide Alarms”).
Typical smoke, fire, and carbon monoxide detectors produce a 3100-3200 Hz pure tone alert signal with the intensity (or power) of 45 to 120 dB (A-weighted for human hearing). The alert signals typically have either a temporal-three (T3) pattern or a temporal-four (T4) pattern. A T3 pattern has three half-second beeps separated by half-second pauses (periods of silence), followed by a 1.5 second pause after the third beep. A T4 pattern, which is commonly used for carbon monoxide detection, has four 0.1-seconds beeps separated by 0.1-seconds pauses, followed by five seconds of silence before the next sequence of four pulses begins.
Studies have shown that the 3100-3200 Hz alert signals generated by existing detector/alert devices are sometimes inadequate for alerting certain classes of individuals. These include children, heavy sleepers, and the hearing impaired. Consequently, commercially available products exists that are capable of listening for a T3 or T4 alert signal, and for generating a supplemental alert signal when a T3 or T4 signal is present. The supplemental alert signal may, for example, include a relatively low frequency audible signal in the range of 400 to 700 Hz, a strobe or other visual signal, or a bed vibration signal. One example of such a product is the Lifetone HL™ Bedside Fire Alarm and Clock available from Lifetone Technology. In addition, new regulations are being considered that would require commercially available detector/alert devices to generate a lower frequency audible alert signal, such as a 520 Hz square wave signal.